Immunosuppressive agents are widely used as a treatment for autoimmune diseases such as rheumatoid arthritis, nephritis, osteoarthritis and systemic lupus erythematosus, chronic inflammatory diseases such as inflammatory bowel disease, and allergic diseases such as asthma and dermatitis. Progress in medicine has led to an increase in the number of tissue and organ transplantations performed each year. In such a situation of modern medicine, having as much control as possible over the rejection following transplantation is a key to successful transplantation. Immunosuppressive agents also play a significant role to this end.
Among immunosuppressors commonly used in organ transplantation are antimetabolites, such as azathioprine and mycophenolate mofetil, calcineurin inhibitors, such as cyclosporin A and tacrolimus, and corticosteroid, such as prednisolone. Despite their popularity, some of these drugs are not effective enough while others require continuous monitoring of the blood drug level to avoid renal failure and other serious side effects. Thus, none of conventional immunosuppressive agents are satisfactory in view of efficacy and potential side effects.
Multiple drug combined-therapy, in which different immunosuppressive drugs with different mechanisms of action are used, is becoming increasingly common with the aims of alleviating the side effects of the drugs and achieving sufficient immunosuppressive effects. Also, development of new types of immunosuppressive agents that have completely different mechanisms of action is sought.
In an effort to respond to such demands, the present inventors conducted a search for new types of immunosuppressive agents with main emphasis on 2-amino-1,3-propanediol derivatives.
While the use of 2-amino-1,3-propanediol derivatives as immunosuppressive agents has been disclosed in PCT publication WO94/08943 (YOSHITOMI PHARMACEUTICAL INDUSTRIES, Ltd., TAITO Co., Ltd.) and in Japanese Patent Publication No. Hei 9-2579602 (YOSHITOMI PHARMACEUTICAL INDUSTRIES, Ltd., TAITO Co., Ltd.), it has not been previously known that 2-amino-1,3-propanediol derivatives having a diaryl sulfide group, which are subjects of the present invention, can serve as an effective immunosuppressor.